I have several static IP’s and recently ran into an issue while changing a few things around. my Trixbox (asterisk) would render only one side of a conversation, resulting in the remote party being able to hear everything, but only silence from any extension in the house. After googling for some time I came across the problem.
Asterisk had lost it’s way because of the external IP change. To prevent this in the future I added this:
externip=x.x.x.x ; ( replacing x.x.x.x with your external IP of course )
in the file /etc/asterisk/sip.conf
a quick restart of asterisk was all that was required to get it going again.
So if you are hearing one side of a conversation and have a NAT + variable or multiple external IP’s, maybe check this out…. for some reason the ‘auto detect external IP’ wouldn’t function correctly on my Trixbox Pro.